Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A typical electron linear accelerator consists of an injector or electron gun, a pre-buncher, a focusing lens, acceleration guides, and an optional target. In the injector, electrons are boiled off the cathode and accelerated toward an annular beam-focusing anode that forms electron bunches. The pre-buncher compacts the electron bunches from the injector. Steering coils in the focusing lens narrow the beam. A set of tuned microwave cavities forms the acceleration guides that are driven by an oscillating electric field. The oscillating electric field can be amplified radio frequency (RF) energy, typically having wave forms or wave shapes of constant-amplitude sine-waves. Then the additional energy from the field accelerates the electrons and increases the electrons' relative mass until they reach the desired energy. Electrons reaching the desired energy are then provided as pulses of electrons as outputs, often provided at a target area of the electron linear accelerator.
This approach has the drawbacks of enabling only a limited amount of customization of the pulses of electrons. Electrical pulses generated by pulse forming networks of current electron linear accelerators typically have the same pulse duration, leading to wasted energy and increased electrical stress when the pulse forming networks are used to generating output pulses of electrons having shorter pulse durations than the pulse duration of electrical pulses from the pulse forming network. Also, current electron linear accelerators require the use of complicated procedures to produce output pulses of having a particular waveform. Further, certain output waveforms are unattainable when using constant amplitude RF signals to provide RF energy to accelerate the electrons.